The present invention is related generally to the field of orthodontics.
Orthodontic treatments involve repositioning misaligned teeth and improving bite configurations for improved cosmetic appearance and dental function. Repositioning is accomplished by applying gentle controlled forces to the teeth over an extended period of time. Due to the limited space within the oral cavity and extensive movements that some teeth must undergo, the teeth will often be moved throughout a series of intermediate patterns to properly arrange the teeth. For example, molars may be temporarily distalized to create adequate space for movement of the incisors. Thus, a single patient may experience an average of 25–30 stages or alignment patterns before achieving the final desired configuration.
Such repositioning may be accomplished with a variety of orthodontic treatments and dental appliances, including conventional braces, spring retainers, positioners, and other removable aligners. With any treatment, an initial mold of the patient's teeth is made. This mold provides a model of the patient's teeth that the orthodontist uses to formulate a treatment strategy. In some instances, it may be desirable to create additional molds of the patient's teeth throughout the treatment plan to reflect individual stages. For example, the treatment strategy may be re-evaluated or a dental appliance may need to be fit to an intermediate tooth configuration.
The need for intermediate tooth configuration molds is particularly significant when using removable elastic appliances to move the teeth. Such elastic appliances typically include a thin shell of elastic material that generally conforms to the pattern of a patient's teeth, but is slightly out of alignment with the initial tooth configuration. By properly choosing the alternate configuration, placement of the elastic appliance over the teeth will move individual teeth to a desired position. Over time, multiple elastic appliances used in successive stages of treatment, will move the teeth to intermediate or final tooth positions. Such a system is described in U.S. Pat. No. 5,975,893, and in published PCT application WO 98/58596 which designates the United States and which is assigned to the assignee of the present application. Both these documents are incorporated by reference for all purposes. When using elastic appliances as described above, a series of appliances are made to reflect the successive stages of treatment. Such appliances are typically made by heating and vacuum or pressure-sealing a sheet of thermoformable plastic over the dentition of a mold.
Traditional methods of dental mold making may be utilized to fabricate a mold for such use. These methods require first forming an impression of the patent's dentition using a suitable impression material, such as alginate or polyvinylsiloxane (PVS). Plaster is then poured into the impression to create a permanent, three-dimensional mold of the dentition. To create an appliance to reflect the next desired tooth configuration in the series of treatment stages, a new mold must be created to reflect the desired configuration. This involves individually cutting the teeth from the mold and resetting the teeth in the desired configuration. Wax is then used to fill in the spaces and represent gingiva. This is a tedious process which compounds both cost and time of treatment for the patient. Resetting is accomplished by either taking into service a laboratory technician or by sending the mold out to a dental laboratory. This process typically requires 2.5 weeks to be accomplished. This represents lost time in the treatment plan as the patient cannot progress to the next stage of treatment until a positioning appliance with the new desired configuration is created. Since such an orthodontic treatment may require, for example, 25 intermediate reset molds to represent 25 stages of treatment progress, the cost and time required for such mold making may be prohibitively high.
The process of iterative mold making may be improved with the use of digital imaging and computer controlled molding systems. Here the patient's initial tooth arrangement and shape of the patient's dental arch are represented by a digital data set. The data set can then be manipulated to reflect progressive tooth arrangements. For each arrangement, the data may be used to guide computerized model fabrication systems to create a corresponding three-dimensional mold. Such techniques may speed production time and reduce costs by eliminating the need for artistic resetting of teeth in mold manufacturing.
Although the above described process aids in the production of iterative molds, further improvement may be desired. The cost in time and materials to produce each mold, though lessened, may still be significant. This cost is additive, as each new stage in treatment or each change in treatment requires the production of a new mold. Likewise, the cost of storing a series of molds for each patient throughout treatment may be formidable. In addition, it may be desirable to visualize a sequence of treatment stages, particularly in an academic environment or in a preliminary patient meeting.
For these reasons, it would be desirable to provide an alternative apparatus and methodology for realizing a series tooth configurations. Such apparatus and methods should be economical, reusable, reduce time consumption, reduce material waste, and, in particular, should reduce the need for fabricating multiple casts of teeth arrangements for stages in the orthodontic treatment. At least some of these objectives, as well as others, are met by the apparatus and methods of the invention described hereinafter.